Bring 1 inch of water to a simmer in a medium saucepan with a steamer basket.
Add the diced tempeh, cover the pot and steam for 10 minutes.
Meanwhile, combine the remaining ingredients in a medium bowl to make the marinade.
When the tempeh is done steaming, transfer it to the bowl with the marinade and toss to coat. Marinate for at least 30 minutes and up to 4 hours.
Preheat the oven to 425°F. Line a baking sheet with parchment paper.
Spread the tempeh out in a single layer on the baking sheet, reserving the excess marinade.
Roast for 10 minutes, coat the tempeh with the remaining marinade, and roast for another 10 minutes, until crisp on all sides. Serve hot.